linux-kernel - Re: [PATCH v2 18/28] thunderbolt: Scan only valid NULL adapter ports in hotplug

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Date:   Tue, 12 Feb 2019 15:04:22 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <YehezkelShB@...il.com>,
        Andreas Noever <andreas.noever@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v2 18/28] thunderbolt: Scan only valid NULL adapter ports
 in hotplug

On Wed, Feb 06, 2019 at 04:17:28PM +0300, Mika Westerberg wrote:
> The only way to expand Thunderbolt topology is through the NULL adapter
> ports (typically ports 1, 2, 3 and 4). There is no point handling
> Thunderbolt hotplug events on any other port.
> 
> Add a helper function (tb_port_is_null()) that can be used to determine
> if the port is NULL port, and use it in software connection manager code
> when hotplug event is handled.

Andreas called these ports TB_TYPE_PORT.  If the official name is NULL,
then renaming to TB_TYPE_NULL might be a useful cleanup.  (Though it
seems the control port, i.e. port 0, is also of type TB_TYPE_PORT?)


> --- a/drivers/thunderbolt/tb.c
> +++ b/drivers/thunderbolt/tb.c
> @@ -344,10 +344,12 @@ static void tb_handle_hotplug(struct work_struct *work)
>  		tb_port_info(port,
>  			     "got plug event for connected port, ignoring\n");
>  	} else {
> -		tb_port_info(port, "hotplug: scanning\n");
> -		tb_scan_port(port);
> -		if (!port->remote)
> -			tb_port_info(port, "hotplug: no switch found\n");
> +		if (tb_port_is_null(port)) {
> +			tb_port_info(port, "hotplug: scanning\n");
> +			tb_scan_port(port);
> +			if (!port->remote)
> +				tb_port_info(port, "hotplug: no switch found\n");
> +		}

There's several other sanity checks further up in this function.
Why not move the tb_port_is_null() check near them, e.g. below the
check for tb_is_upstream_port()?

Thanks,

Lukas